Several of the currently available engineering design and software analysis packages are being utilized by designers in the early stages of the product life cycle for product modeling and evaluation. However, while the growing need for designing 'sustainable' products is increasingly being recognized, an overall lack of measurement tools and formal methods for sustainability assessment remains a void to be addressed. In order to provide a reliable and design-based evaluation approach, "product footprint" is proposed as a viable sustainability assessment metric for gauging the environmental impacts of products. Such an assessment system would give direct feedback to designers of the overall manufacturing impact, so that design modifications can be effected to minimize environmental costs while maintaining product quality and design intent. Further, since all the product structure information is needed throughout the entire product life cycle, the system must be capable of making such evaluations in a PLM environment. A methodology for computing an energy metric and thereby overall manufacturing footprint for sustainability assessment is developed using the Pro/ENGINEER CA D system for design and Pro/NC-MILL for detailed NC path planning for machining operations.